The engine -- outsourced from Yamaha -- may be stressed structurally, but with a claimed 48 horsepower at 5250 RPM it's definitely not stressed in the horsepower department. The carburetion on our test bike seemed off at lower revs, but cleared up once the tach passed 4000; unfortunately, by the time you reach this point you've already stumbled through the bottom and mid-range of the power band. After all, the motor only winds out to 6800 RPM.